The present invention relates to a balance weight receivable in a balance weight groove in turbomachinery, for example, a steam turbine, methods of remotely installing the balance weight in the groove without removal of turbomachinery casing and tools for installing the balance weight within the groove.
In the manufacture of turbomachinery, for example, steam turbines, final balancing of the rotating component is an essential and important step. Also, at several times during the life of a steam turbine, it is usually necessary to rebalance the rotating component. This is typically accomplished by adding weights to the rotors to compensate for the rotational effects of a bowed rotor, missing or modified rotor components such as buckets or covers, or to lower the vibration levels at which the unit is operating. Weight grooves used to balance rotors during manufacture of a turbine conventionally have a T-shaped or dovetail configuration. Access ports through the casing are typically not provided in older turbines. The weights manufactured as original equipment in such turbines are usually dovetail or T-shaped in configuration and require staking to fix the weights to the rotary component. For balance weight grooves that are intended for rebalancing during service, access ports are typically provided through the casings and the balance weights are usually of a screw plug type.
To convert a rotor that had only a factory balance weight provision to one capable of field balancing, it is necessary to increase the volume of material available for the installation of screw-type plug weights by welding. This process was very time-consuming and expensive. Additionally, the welding process, because of the input of heat to the rotor forging, required that the material be stress-relieved after welding. Re-machining of many of the tight fits on the rotor body was also frequently necessary after the welding and stress relief. This process was also expensive as the rotor required removal from the turbine before the necessary machining tools could be utilized to effect the changes. Also, the casing needed to be modified to provide an access port through which field balance weights could be installed in the rotor. Consequently, there is a need to provide a balance weight/groove combination for both factory and field installation, a method of installing the balance weight in the groove and tools for effecting the installation.
In accordance with a preferred embodiment of the present invention, there is provided a balance weight for insertion in a groove of a rotating component, for example, a rotor of turbomachinery. Preferably, the groove has a wedge or dovetail configuration or a T-shaped slot. Particularly, the balance weight has a configuration generally complementary to the cross-sectional configuration of the groove. Characteristically, outer and inner wall portions of each type of groove are spaced respective first and second distances from one another, with the second distance being greater than the first distance. The balance weight has first margins having a first dimension less than the first distance, enabling the balance weight in a first orientation to be inserted into the groove. The balance weight also has second margins having a second dimension greater than the first distance such that, upon rotation of the balance weight in the groove into a second orientation, the second margins lie within the groove inwardly of the outer wall portions of the groove. Additionally, a screw is threaded through the balance weight. By threading the screw with the balance weight in the groove, the balance weight is elevated within the groove to engage the second margins of the balance weight against the opposing outer walls of the groove to retain the balance weight within the groove. With the balance weight thus engaged, the balance weight can be staked to the rotor and the screw staked to the balance weight.
To install the balance weight, an installation tool is inserted through access openings in the casing and releasably carries the balance weight at a distal end of the tool for insertion into the groove. The insertion tool comprises an elongated body, preferably tubular, having at least one and preferably two rods, generally coextensive with the body and which rods are rotatable for screwthreaded engagement with female threaded sockets on the balance weight such that the balance weight can be disposed within the turbomachinery through an access opening in its casing by the installation tool and inserted in the groove. The insertion tool also includes a head shaped for reception in a complementary-shaped slot on the balance weight whereby, by rotating the insertion tool, the balance weight can be rotated within the groove from its first orientation to its second orientation to locate the second margins below the outer wall portions. The insertion tool also includes a central opening through its body through which is received an elongated driver. The driver has a head for engaging the screw of the balance weight. By rotating the driver and hence the screw, the balance weight is elevated within the groove such that the second margins engage the outer wall portions of the groove to clamp the balance weight to the rotor against circumferential, rotational and radial movement. The insertion tool is then detached from the balance weight by unthreading the rod(s) from the balance weight and withdrawn through the access opening. Subsequently, a staking tool is inserted through the access openings. The staking tool has a pair of staking projections for staking the balance weight and the rotor component to one another. The staking tool also includes another staking projection to stake the balance weight and screw to one another.
In a preferred embodiment according to the present invention, there is provided apparatus for balancing a rotational component about an axis of rotation, comprising a rotor having a generally circumferentially extending groove at least in part about the axis of rotation, opposing walls of the groove having inner and outer portions with the outer wall portions spaced a first distance from one another and the inner wall portions spaced a second distance from one another greater than the first distance, a balance weight having first margins with a first dimension less than the first distance enabling the balance weight, in a first orientation relative to the groove, for reception in the groove, the balance weight having second margins with a second dimension greater than the first dimension and the first distance such that, upon rotation of the balance weight in the groove to a second orientation relative to the groove, the second margins lie within the groove inwardly of and in registration with the outer wall portions and a screw threadedly received in the balance weight and engageable with a base of the groove, the balance weight being displaceable away from the base in response to rotation of the screw relative to the balance weight to engage the second margins against the outer wall portions to retain the balance weight in the groove against circumferential and outward movement thereof relative to the groove.
In a further preferred embodiment according to the present invention, there is provided for use in balancing a rotor about an axis of rotation wherein the rotor has a generally circumferentially extending groove extending at least in part about the axis of rotation, a balance weight, comprising a balance weight body having first margins opposite one another and spaced from one another a first dimension enabling the balance weight body for reception in the groove, the balance weight body having second margins opposite one another and spaced from one another a second dimension greater than the first dimension for disposition within the groove, the fist and second margins of the balance weight body being generally oriented 90xc2x0 relative to one another about the body and a screw threadedly received in the balance weight for engaging a base of the groove, the balance weight body having an outer face with a slot for receiving a tool to rotate the balance weight.
In a still further preferred embodiment according to the present invention, there is provided a method of remotely installing a balance weight in a groove of a rotary component in turbomachinery having at least one casing surrounding the rotary component, comprising the steps of attaching a balance weight to the end of an elongated insertion tool, inserting the balance weight and tool through an access opening in the casing, locating the balance weight in the balance weight groove using the insertion tool, rotating the balance weight in the groove to register marginal portions of the balance weight below marginal wall portions of the groove, securing the balance weight in the groove by threading a screw through the balance weight to engage the base of the groove and engage the marginal portions of the balance weight against the marginal wall portions of the groove, detaching the tool from the balance weight and withdrawing the tool through the access opening.
In a still further preferred embodiment according to the present invention, there is provided an insertion tool for remotely inserting a balance weight through an access opening in a casing of turbomachinery into a groove of a rotary component thereof and rotating the balance weight within the groove, comprising an elongated tool body having a handle at a proximal end, a central opening through the tool body, and a tool head at an opposite distal end for engaging and rotating the balance weight, a pair of rods carried by the body straddling the central opening and rotatable relative to the tool body for releasable securement at distal ends to the balance weight, the handle enabling rotation of the tool body and the rods to rotate the balance weight in the groove.
In a still further preferred embodiment according to the present invention, there is provided a kit for remotely inserting a balance weight through an access opening in a casing of turbomachinery into a groove of a rotary component thereof and securing the balance weight within the groove, comprising an elongated tool body having a handle at a proximal end, a central opening through the body, and a tool head at an opposite distal end for engaging and rotating the balance weight, a pair of rods carried by the body straddling the tool body and rotatable relative to the tool body for releasable securement at distal ends to the balance weight, a driver receivable within the central opening for rotating a screw to engage the balance weight against marginal walls of the groove to secure the balance weight within the groove and a staking tool comprising an elongated staking tool body terminating at a distal end in a staking projection for staking the balance weight and rotary component to one another.